In states that do not expand Medicaid: 90% of uninsured individuals below 138% of the federal poverty level (FPL)—the eligibility level for Medicaid expansion—would remain uninsured after 2014, as well as 75% of the uninsured individuals above the eligibility level.

In states that do expand Medicaid: 40%of Medicaid-eligible residents who are currently uninsured will remain uninsured, as well as 60% of uninsured individuals above the eligibility level.

Using our Medicaid Map, we determined which states will (or likely will) expand Medicaid—based on governors' definitive statements or the expansion's legislative status—and which states will not (or likely will not) expand Medicaid.

Using that determination, the Harvard projections, and 2012 Census data, we estimated each state's rate of uninsured residents following the ACA's coverage expansion.

Editor's Note: As lawmakers and governors take action on coverage expansion, expected uninsurance rates will change. For the most up-to-date version of the map, check out our interactive Medicaid expansion map.

Which states will have the most uninsured residents?

Based on our analysis, the five states that are expected to have the highest uninsurance rates after the ACA rollout are:

Texas (where 191.3 in every 1,000 residents will not have insurance);

Louisiana (167.8 in every 1,000 residents);

Georgia (155.3 in every 1,000 residents);

South Carolina (152.6 in every 1,000 residents); and

Alaska (142.2 in every 1,000 residents).

It's worth noting that these states are not expected to participate in the ACA expansion, although Alaska's governor has not definitively stated his position on the issue. If Texas changes its mind and opts into the ACA's Medicaid expansion, the state's uninsurance rate would drop to approximately 118 per 1,000 residents, according to the Harvard projections.

Which states will have the fewest uninsured residents?

Meanwhile, the states that are expected to have the lowest uninsurance rates after the ACA rollout are:

Massachusetts (where just 16.9 in every 1,000 residents will not have insurance);

Hawaii (38.1 in every 1,000 residents);

District of Columba (42.7 in every 1,000 residents);

Connecticut (45.1 in every 1,000 residents); and

North Dakota (45.7 in every 1,000 residents).

Unsurprisingly, all five of these states are expected to participate in the ACA expansion.

Which states have the most to gain?

Generally speaking, the states that gain the most from the ACA's coverage expansion are states that currently have high uninsurance rates. They are also more likely to reduce their uninsurance rates if they participate in the Medicaid expansion, for obvious reasons.

Nevada—which is expected to expand Medicaid—will benefit the most from coverage expansion; the state is expected to see a 50.25% reduction in its uninsured population. Nonetheless, the state likely will maintain a relatively high rate of uninsured residents, with about 109.5 in every 1,000 residents going without insurance.

Arkansas, Kentucky, and Missouri are the other states expected to gain the most from expansion.

Meanwhile, the 10 states expected to gain the least from coverage expansion all are unlikely to expand Medicaid. Alabama, Mississippi, and Georgia are the three states that are expected to see the smallest drop in their uninsured population after 2014.

Want to know more about the ACA's coverage expansion?

In 2014, the ACA's Medicaid expansion and health insurance exchanges will go live, expanding insurance to millions of Americans.

The insurance exchanges: Register for our July webconferences to learn everything you need to know about the insurance marketplaces before they begin enrolling patients on Oct. 1. For an immediate look, check out our new white paper.

The Medicaid expansion: Listen to this on-demand webconference to learn how to manage your hospital's new Medicaid population.